The present project possesses two long-term objectives. The first is to determine empirically the role of attention in adult age differences in one category of cognitive performance, visual search and classification tasks. The second is to investigate the potential influence of health status (specifically, mild essential hypertension) on age-%elated changes in attentional processes. Experiments 1-12 in the present project will compare the performance of relatively healthy. community-- dwelling young and older adults on visual search and classification tasks. These tasks require that subjects make, on each trial, a choice response regarding whether a target item (from a pre-assigned set) is present in a visual display. Experiments 1-4 will examine age differences in the allocation of attention within a trial. These four experiments will test a quantitative model in which the time required to allocate attention to a cued display location is independent (within limits) of the distance of this location from fixation. Experiments 5-9 will examine age differences in the allocation of attention across trials. An issue to be addressed in these five studies is whether a single quantitative model can incorporate the effects of target-identity cuing, as well as the effects of display-location cuing. Experiments 10-12 will be concerned with the composition of the display items rather than with the dynamic properties of attentional allocation. In these three experiments, the confusability of the target and nontarget items will be varied, and theoretical accounts based on stimulus similarity and feature integration will he compared. Experiments 13 and 14 will investigate the potential interaction of age and health status in visual search performance. These two studies will include subjects with mild essential hypertension, as well as normotensive individuals. A question of interest in these two experiments is whether the pattern of age-related decline in attentional processing will be evident at a younger age for hypertensives than for normotensives. The present project is designed to improve current theoretical accounts of age-related change in cognitive functioning and to provide new information on the contribution of health status to this age-related change.